Chronic low back pain patients aged 21 to 60 needed for a research study of the effects of transcranial direct current stimulation (tDCS) on the analgesic effects of lidocaine cream as measured by functional Magnetic Resonance Imaging (fMRI). Study will be conducted on nine separate days not requiring an overnight stay in the hospital.

Inclusion Criteria:

• Volunteers 21-60 years of age.
• Meets the Classification Criteria of chronic LBP (having low back pain for more than 6 months), as determined by the referring physician.
• At least 4/10 clinical pain on the 11-point LBP VAS (criteria recommended by Dworkin et al.)
• At least a 10th grade English-reading level; English can be a second language provided that the patients understand all questions used in the assessment measures.

Exclusion Criteria:

• Specific causes of back pain (e.g., cancer, fractures, spinal stenosis, infections).
• Complicated back problems (e.g., prior back surgery, medicolegal issues).
• The intent to undergo surgery during the time of involvement in the study.
• History of cardiac, respiratory, or nervous system disease that, in the investigator's judgment, precludes participation in the study because of a heightened potential for adverse outcome. For example: asthma, claustrophobia, epilepsy or acute eczema under the electrodes.
• Presence of any contraindications to MRI scanning. For example: cardiac pacemaker, metal implants, claustrophobia, pregnancy, cannot lie still in an fMRI scanner.
• History of medical or psychiatric illness.
• History of substance / alcohol abuse or dependence.